Aki Toyosaki (born October 28, 1986 in Tokushima Prefecture, Japan) is a Japanese actress and singer. She had her first major voice acting roles in 2007, voicing Amuro Ninagawa in Kenkō Zenrakei Suieibu Umishō and Su in Shugo Chara! however, her career as a musician began after she recorded the opening and ending themes of the anime series K-On! in April 2009. Forming a quartet with Ayahi Takagaki, Haruka Tomatsu, and Minako Kotobuki to record "Future Stream" from First Love Limited, the group rebranded as Sphere, and the theme was released as the group's first single on April 22, 2009. They went on to record other songs, including the opening theme "Super Noisy Nova" for Sora no Manimani, released as a single in July 2009, and "It Raises the Wind/Brave My Heart" in November 2009. Her debut single "love your life" was released in October 2009, reaching number 12 on the Oricon charts, and featured on the album Love Your Life, Love My Life (2011), along with “Dill,” and "Shun Pu" (春風) which went to number 14 and 5 respectively. She followed this with another five albums including: Love Letters (2013), All Time Lovin’ (2016), Love Your Best (2017), AT Living (2018), and Caravan! (2021) which spawned myriad singles over the years including "Music" (2012), "Kanae Tamae" (叶えたまえ) (2014), and "Honey and Loops," all of which placed in the top 20 of Oricon's weekly charts. In 2024, she reunited with Ayahi Takagaki to release the EP トゥインクルクス, led by its title track, which climbed to number 26 on the Oricon Top 50 charts.